Ramaz Lomsadze - Academia.edu (original) (raw)

Papers by Ramaz Lomsadze

Research paper thumbnail of Interference Effects in Fully Differential Ionization Cross Sections near the Velocity Matching in P + He Collisions

Atoms

We performed a fully differential experimental and theoretical study on ionization of He in inter... more We performed a fully differential experimental and theoretical study on ionization of He in intermediate-energy collisions with protons for a small projectile coherence length. Data were taken for an ejected electron energy corresponding to a speed close to the projectile speed (velocity matching). In the fully differential angular electron distributions, a pronounced double-peak structure, observed previously for a coherence length much larger than the atomic size, is much less pronounced in the current data. This observation is interpreted in terms of interference between first-and higher-order transition amplitudes. Although there is large quantitative disagreement between experiment and theory, the qualitative agreement supports this interpretation.

Research paper thumbnail of Fully differential single ionization cross sections in 75 keV p + He collisions near the velocity matching

Bulletin of the American Physical Society, 2019

Research paper thumbnail of Charge-exchange, ionization and excitation in low-energy Li$^{+}-$ Ar, K$^{+}-$ Ar, and Na$^{+}-$He collisions

arXiv: Atomic Physics, 2016

Absolute cross sections are measured for charge-exchange, ionization, and excitation within the s... more Absolute cross sections are measured for charge-exchange, ionization, and excitation within the same experimental setup for the Li$^{+}-$Ar, K$^{+}-$ Ar, and Na$^{+}-$ He collisions in the ion energy range 0.5−100.5-100.5−10 keV. Results of our measurements along with existing experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes are realized with high probabilities and electrons are predominately captured in ground states. The cross section ratio for charge exchange, ionization and excitation processes roughly attains the value 10:2:110:2:110:2:1, respectively. The contributions of various partial inelastic channels to the total ionization cross sections are estimated and a primary mechanism for the process is defined. The energy-loss spectrum, in addition, is applied to estimate the relative contribution of different inelastic channels and to determine the mechanis...

Research paper thumbnail of Differential Study of Projectile Coherence Effects on Double Capture Processes in p + Ar Collisions

Atoms, 2020

We have measured differential yields for double capture and double capture accompanied by ionizat... more We have measured differential yields for double capture and double capture accompanied by ionization in 75 keV p + Ar collisions. Data were taken for two different transverse projectile coherence lengths. A small effect of the projectile coherence properties on the yields were found for double capture, but not for double capture plus ionization. The results suggest that multiple projectile–target interactions can lead to a significant weakening of projectile coherence effects.

Research paper thumbnail of Study of inelastic processes in Li⁺- Ar, K⁺- Ar, and Na⁺-He collisions in energy range 0.5--10 keV

Journal of Physics B: Atomic, Molecular and Optical Physics, 2017

Absolute cross sections are measured for charge-exchange, ionization, and excitation processes wi... more Absolute cross sections are measured for charge-exchange, ionization, and excitation processes within the same experimental setup for the LiAr, KAr, and NaHe collisions in the ion energy range of 0.5–10 keV. The results of the measurements and schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes occur with high probabilities and electrons are predominantly captured in ground states. The contributions of various partial inelastic channels to the total ionization cross section are estimated, and a primary mechanism for the process is identified. In addition, the energy-loss spectrum is applied in order to estimate the relative contribution of different inelastic channels, and to determine the mechanisms for the ionization and for some excitation processes of Ar resonance lines for the Ar collision system. The excitation cross sections for the helium and for the sodium doublet lines for the NaHe collision system both reveal some unexpected features. A mechanism to explain this observation is suggested.

Research paper thumbnail of Ionization, charge exchange, and excitation during collisions of sodium ions with argon

Research paper thumbnail of Excitation of Meinel and the first negative band system at the collision of electrons and protons with the nitrogen molecule

Research paper thumbnail of Precision measurements of cross-sections for inelastic processes in collisions of alkali metal ions with atoms of rare gases

International Journal of Modern Physics B, 2017

A multifaceted experimental study of collisions of Na[Formula: see text] and K[Formula: see text]... more A multifaceted experimental study of collisions of Na[Formula: see text] and K[Formula: see text] ions in the energy range of 0.5–10 keV with He and Ar atoms is presented. Absolute cross-sections for charge-exchange, ionization, stripping and excitation processes were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss and optical spectroscopy methods. The experimental data and the schematic correlation diagrams are employed to analyze and determine the mechanisms for these processes.

Research paper thumbnail of Ionization, charge exchange, and excitation during collisions of sodium ions with argon

Technical Physics, 2007

The absolute values of cross sections of ionization, charge exchange, and excitation during Na +-... more The absolute values of cross sections of ionization, charge exchange, and excitation during Na +-Ar collisions are measured in the ion energy range 0.5-10.0 keV. Experiments are performed by a modified method of transverse electric field and by the optical spectrometry method. The mechanisms for realization of inelastic channels are explained qualitatively on the basis of a schematic correlation diagram of diabatic quasi-molecular energy levels of a system of colliding particles. The quasi-molecular nature of interaction is revealed for excitation processes. The excitation mechanisms of collision partners are established. A noticeable contribution to the excitation of the 4 s state of the argon atom comes from the cascade transition from upper-lying 4 p and 3 d levels. An oscillatory structure is observed in the excitation functions of atomic lines of ArI (104.8 and 106.7 nm). The shape of the curve describing the dependence of the charge-exchange cross section on the collision energy is explained by the presence of two nonadiabaticity regions. In the low-energy region (up to E = 2 keV), charge exchange is due to electron capture to the ground state as a result of Σ-Σ transitions, while Σ-Π transitions associated with the rotation of internuclear axis play the leading role in charge exchange in the energy range E > 3 keV. The contribution of a number of inelastic channel is estimated for the ionization process. It is found that the main contribution to ionization is associated with the decay of self-ionization states in an isolated atom.

Research paper thumbnail of Interference Effects in Fully Differential Ionization Cross Sections near the Velocity Matching in P + He Collisions

Atoms

We performed a fully differential experimental and theoretical study on ionization of He in inter... more We performed a fully differential experimental and theoretical study on ionization of He in intermediate-energy collisions with protons for a small projectile coherence length. Data were taken for an ejected electron energy corresponding to a speed close to the projectile speed (velocity matching). In the fully differential angular electron distributions, a pronounced double-peak structure, observed previously for a coherence length much larger than the atomic size, is much less pronounced in the current data. This observation is interpreted in terms of interference between first-and higher-order transition amplitudes. Although there is large quantitative disagreement between experiment and theory, the qualitative agreement supports this interpretation.

Research paper thumbnail of Fully differential single ionization cross sections in 75 keV p + He collisions near the velocity matching

Bulletin of the American Physical Society, 2019

Research paper thumbnail of Charge-exchange, ionization and excitation in low-energy Li$^{+}-$ Ar, K$^{+}-$ Ar, and Na$^{+}-$He collisions

arXiv: Atomic Physics, 2016

Absolute cross sections are measured for charge-exchange, ionization, and excitation within the s... more Absolute cross sections are measured for charge-exchange, ionization, and excitation within the same experimental setup for the Li$^{+}-$Ar, K$^{+}-$ Ar, and Na$^{+}-$ He collisions in the ion energy range 0.5−100.5-100.5−10 keV. Results of our measurements along with existing experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes are realized with high probabilities and electrons are predominately captured in ground states. The cross section ratio for charge exchange, ionization and excitation processes roughly attains the value 10:2:110:2:110:2:1, respectively. The contributions of various partial inelastic channels to the total ionization cross sections are estimated and a primary mechanism for the process is defined. The energy-loss spectrum, in addition, is applied to estimate the relative contribution of different inelastic channels and to determine the mechanis...

Research paper thumbnail of Differential Study of Projectile Coherence Effects on Double Capture Processes in p + Ar Collisions

Atoms, 2020

We have measured differential yields for double capture and double capture accompanied by ionizat... more We have measured differential yields for double capture and double capture accompanied by ionization in 75 keV p + Ar collisions. Data were taken for two different transverse projectile coherence lengths. A small effect of the projectile coherence properties on the yields were found for double capture, but not for double capture plus ionization. The results suggest that multiple projectile–target interactions can lead to a significant weakening of projectile coherence effects.

Research paper thumbnail of Study of inelastic processes in Li⁺- Ar, K⁺- Ar, and Na⁺-He collisions in energy range 0.5--10 keV

Journal of Physics B: Atomic, Molecular and Optical Physics, 2017

Absolute cross sections are measured for charge-exchange, ionization, and excitation processes wi... more Absolute cross sections are measured for charge-exchange, ionization, and excitation processes within the same experimental setup for the LiAr, KAr, and NaHe collisions in the ion energy range of 0.5–10 keV. The results of the measurements and schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes occur with high probabilities and electrons are predominantly captured in ground states. The contributions of various partial inelastic channels to the total ionization cross section are estimated, and a primary mechanism for the process is identified. In addition, the energy-loss spectrum is applied in order to estimate the relative contribution of different inelastic channels, and to determine the mechanisms for the ionization and for some excitation processes of Ar resonance lines for the Ar collision system. The excitation cross sections for the helium and for the sodium doublet lines for the NaHe collision system both reveal some unexpected features. A mechanism to explain this observation is suggested.

Research paper thumbnail of Ionization, charge exchange, and excitation during collisions of sodium ions with argon

Research paper thumbnail of Excitation of Meinel and the first negative band system at the collision of electrons and protons with the nitrogen molecule

Research paper thumbnail of Precision measurements of cross-sections for inelastic processes in collisions of alkali metal ions with atoms of rare gases

International Journal of Modern Physics B, 2017

A multifaceted experimental study of collisions of Na[Formula: see text] and K[Formula: see text]... more A multifaceted experimental study of collisions of Na[Formula: see text] and K[Formula: see text] ions in the energy range of 0.5–10 keV with He and Ar atoms is presented. Absolute cross-sections for charge-exchange, ionization, stripping and excitation processes were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss and optical spectroscopy methods. The experimental data and the schematic correlation diagrams are employed to analyze and determine the mechanisms for these processes.

Research paper thumbnail of Ionization, charge exchange, and excitation during collisions of sodium ions with argon

Technical Physics, 2007

The absolute values of cross sections of ionization, charge exchange, and excitation during Na +-... more The absolute values of cross sections of ionization, charge exchange, and excitation during Na +-Ar collisions are measured in the ion energy range 0.5-10.0 keV. Experiments are performed by a modified method of transverse electric field and by the optical spectrometry method. The mechanisms for realization of inelastic channels are explained qualitatively on the basis of a schematic correlation diagram of diabatic quasi-molecular energy levels of a system of colliding particles. The quasi-molecular nature of interaction is revealed for excitation processes. The excitation mechanisms of collision partners are established. A noticeable contribution to the excitation of the 4 s state of the argon atom comes from the cascade transition from upper-lying 4 p and 3 d levels. An oscillatory structure is observed in the excitation functions of atomic lines of ArI (104.8 and 106.7 nm). The shape of the curve describing the dependence of the charge-exchange cross section on the collision energy is explained by the presence of two nonadiabaticity regions. In the low-energy region (up to E = 2 keV), charge exchange is due to electron capture to the ground state as a result of Σ-Σ transitions, while Σ-Π transitions associated with the rotation of internuclear axis play the leading role in charge exchange in the energy range E > 3 keV. The contribution of a number of inelastic channel is estimated for the ionization process. It is found that the main contribution to ionization is associated with the decay of self-ionization states in an isolated atom.